Control device

ABSTRACT

A control device wherein a pressure sensitive element displaceable by pressure variations, transmits linear motion to a balance plate. Stops associated with the balance plate define a pair of axes about which the balance plate alternately pivots. The device includes a single control such as a microswitch having a single actuator displaceable between first and second positions corresponding to mutually cancelling control modes. Pivotal movement of the balance plate about one axis effects movement of the actuator through the first position while pivotal movement about the other axis effects movement of the actuator through the second position. The pressures at which the respective positions are attained can be independently determined by adjustable springs acting on the balance plate and through the respective axes.

United States Patent Weber 14 1 Feb. 18, 1975 CONTROL DEVICE [76] Inventor: Ernesto Juan Weber, No. 470 State Pr'mary hammer-Paul Maslousky of the Federal District Lluvia, N Attorney, Agent, 1)) FlrmBZlCOl'l & Thomas Mex.

221 Filed: Jan. 11, 1974 [57] ABSTRACT A control device wherein a pressure sensitive element [211 App! 432460 displaceable by pressure variations, transmits linear Related U.S. Application Data motion to a balance plate. Stops associated with the [60] Division of sei N0. 236,732, March 21, 1972, Pat. balance Plate define a P Of axes about which the No. 3,786,212, which is a Continuation-impart of s balance plate alternately pivots. The device includes a No. 154,536, June 18, 1971, abandoned. single control such as a microsw'itch having a single actuator displaceable between first and second posi- [52] U.S. Cl 92/95,92/133, 92/99 tions corresponding to mutually cancelling control [51] Int. Ql. F01!) 19/00, FOlb 31/00, F16j 3/00 modes. Pivotal movement of the balance plate about [58] Field of Search 92/130, 133, 95, 94 one axis effects movement of the actuator through the first position while pivotal movement about the other [56] References Cited axis effects movement of the actuator through the sec- UNITED STATES PATENTS ond position. The pressures at which the respective 2 014 541 (H1935 wa at 92/95 positions are attained can be independently deter- 2726'090 12/1955 wilifimiiij31:1::31?""""iijiiiii'iz/i3O misss by sdisssssls springs sssisg on the sslssss 3:047:341 7/1962 Alfieri 92/130 Plate and through the respective axes- 3,227,494 1/1966 Alfieri 92/l30 3,386,297 6/1968 Willis 92/130 2 9 D'awmg F'gures 1 CONTROL DEVICE This is a division of application Ser. No. 236,732, filed Mar. 21, I972, now U.S. Pat. No. 3,786,212, which application is hereby incorporated by reference and which is a continuation-in-part of United States application Ser. No. 154,536, filed on June 18, 1971, now abandoned.

BACKGROUND AND OBJECTS OF THE INVENTION 1. Field of the Invention This invention relates to a control device, and, in particular, a control device in the form of a pressure switch. The device includes an expansible chamber having a pressure sensitive element, such as a diaphragm, displaceable by variations in pressure. The pressure sensitive element actuates a control means, such as a microswitch, to produce a control signal in response to the pressure variation.-

In the present type of device, the pressure sensitive element is coupled to a balance means which in turn, is coupled to a pair of biasing means or springs which urge the balance means in a direction opposing expansion of the chamber. The resulting diaphragm displacement is transmitted to the balance means, causing the balance means to move against the force of the weaker spring. This movement is a pivotal movement about a first stop or abutment located opposite the weaker spring. The balance means is held against this stop by the heavier spring. The pivotal movement continues until the moving portion of the balance means adjacent the weaker spring engages a second stop. At this point, the balance means is at the midpoint of its overall movement, further movement about the first stop being prevented by the second stop. When pressure is sufficiently great to overcome the bias of the heavier spring, the balance means begins to pivot about the second stop until it reaches its extreme high pressure position.

As the pressure decreases from the extreme high pressure point, the balance means will, of course, again pivot-about the second stop, under the bias of the heavier spring, but in the opposite rotational direction until the middle position is again reached. At the middle position, the balance means is restrained by the first stop from further pivotal movement about the second stop. When the pressure drops sufficiently, the balance means will again pivot about the first stop under the bias of the weaker spring. This movement continues until the balance means reaches its extreme low pressure position.

The type of movement described above, and apparatus for effecting the same, will hereinafter be referred to as alternating fulcrum movement and alternating fulcrum apparatus.

In many pressure switch applications, it is desirable to provide a pressure differential between two different modes of actuation, for example, an on mode and an of mode. The use of an alternating fulcrum device is ideal in this context, for the movement of the balance means about one of the alternating fulcrums can control the on actuation and the movement about the other fulcrum can control the of deactuation. Even more advantageous is the fact that the biasing means can be made adjustable to control the movement of the balance means and to concomitantly control the pressure values at which the switch is actuated or deactuated. Therefore, the use of an alternating fulcrum device having adjustable biasing means coupled to a balance means allows independent adjustment of the switch on" and off points to practically any value in the overall operating range of the switch.

While the type of device'contemplated has been and will be referred to as a pressure switch, it will be understood that the present invention can be equally well adapted to a vacuum responsive device, a temperature responsive device using a confined fluid, or a differential pressure responsive device.

2. Description of the Prior Art The use of an alternating fulcrum movement per se in a pressure switch is known in the art.

U.S. Pat. Nos. 2,284,940; 2,266,144; and 2,274,119 to A.E. Baak all disclose such devices. In these patents, as well as in all true alternating fulcrum devices, it is necessary that at least two stop or abutment means be disposed on opposite sides of the balance means from each other. The points of engagement of the stop means or abutments form the fulcrums or axes about which the balance means pivots. Since the biasing means must also be connected with at least one side of the balance means, it becomes a problem to make the lines of action of the spring forces pass through the fulcrums or axes. This is true because, in the prior art devices, both the biasing means and the'stop means on one side of the balance means will interfere with each other if located in the same path. It is important that the forces of each of the biasing means pass through their adjacent fulcrums, because, if they do not, both biasing means will influence the movement of the balance means about each fulcrum. Since the separate springs are intended to independently determine the different points of response, this influence is detrimental to the proper functioning of the device. The first above-mentioned patent expresses the desirability of making the biasing force act through the fulcrum, but examination of the disclosures in all the above patents makes it clear that the result sought after has not been achieved. In all three patents, the spring force acts at a point offset from the adjacent fulcrum so that an undesirable, extraneous rotative force will always be exerted on the balance means.

In the first reference mentioned above, adjustment of the biasing means is made from the same side of the unit as that on which the pressure inlet is located. Clearly, in many situations, this could make adjustment difficult or impossible. The last two mentioned references above provide for adjustment from positions spaced from the pressure inlet, but this is accomplished only through complex lever, linkage or transmission systems which in turn account for large, bulky and complex units.

U.S. Pat. No. 2,766,349 to Hamburg also discloses an alternating fulcrum pressure switch. An important drawback here is that the springs of different strengths are not adjustable and this independent adjustment or different settings is not possible. While it appears that, in an indirect manner, the biasing forces may be made to act through the pivot points of the balance means, the forces are transmitted through mechanical means which clearly will introduce substantial friction, and thus extraneous forces will also be a problem here. Also, in Hamburg, it is necessary to use two microswitches, one at each end of the balance means, to obtain a substantial differential between actuation points.

US. Pat. No. 3,210,486 to Holzer discloses an alternating fulcrum device, or more precisely, an alternating axis device. The arrangement is such that the biasing forces do not act on the axes at all times.

U.S. Pat. No. 2,790,044 to Booth discloses another device, which, broadly speaking might be considered to disclose movement about two axes to effect switch actuation. Here the biasing means is non-adjustable and acts on the balance means at a location clearly remote from the pivoting axes.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a control device of the foregoing type of improved and simplified construction, embodying relatively few operating parts and which can be built at a relatively low cost with a very compact configuration.

It is a further object of the invention to provide a control device wherein at least two distinct control points can be made independently adjustable over a large range, and more particularly, a device which can provide such adjustability when coupled with a single microswitch, or similar control means, having a single actuator.

It is another object of the invention to provide an alternating fulcrum or alternating axis control device having a pair of adjustable biasing means which act independently from each other.

It is an additional object of the invention to provide an alternating fulcrum or alternating axis device wherein the lines of force of the adjustable biasing means act through the fulcrums or axes.

Another object is the provision of a connection and- /or linkage means between the balance means and the microswitch or control means, which linkage and/or connection means is simple, reliable and economical and which comprises relatively few parts.

A further object of the invention is the provision of a simple, inexpensive lost motion means between the balance means and microswitch or control means to compensate for different ranges of displacement of the balance means and of the actuator of the control means;

Another'objectis the provision of an alternating axis device wherein the axes nearly intersect at a pivotal set of stops, the effective connection point of the balance means to the control means being at a point on the balance means whereby the control means is not influenced by minute displacements of the balance means at the pivotal set of stops.

Yet another object is the provision of a control device having a piston and a diaphragm which are interconnected, and a means associated with the diaphragm for eliminating friction between the piston and its associated cylinder.

Other objects and advantages will be apparent from or pointed out in the following description and accompanying drawings.

SUMMARY OF THE INVENTION The present invention overcomes the difficulties found in the prior art devices by providing an adjustable biasing means whose lines of force act directly through each fulcrum or axis of the balance means. In one embodiment, this is accomplished by providing a balance means in the form of a beam with recessed portions at each end. Each recess provides additional surfaces on the balance means whereby the stop means and biasing means may be aligned with each other.

In another embodiment, the balance means takes the form of a plate which pivots about two alternating axes, each axis being defined by stops which are spaced from each other. With this arangeement, it is possible to locate the biasing means between the stops and yet position each biasing means so as to act directly on one axis. This latter arrangement has the advantage of providing much greater stability and reliability than can be obtained from a beam arrangement, and the added stability permits the use of compression coil springs as biasing means.

Compression springs have the advantage that they can be most readily positioned on the side of the balance plate opposite to the pressure sensing means and associated pressure inlet. Clearly, in most circumstances access to the switch will be easier from the side opposite the inlet. Thus, with compression springs, adjustments to the spring forces (and thus the response characteristics of the switch) can be made from the side opposite to the inlet. Also, when tension springs are used, mechanisms to permit rotation of the adjustment screws with respect to their associated springs are required. With the use of compression springs, no such mechanisms are required, since the springs themselves are free to rotate. The use of coil springs in compression is made more practical by the addition of special spring guides to prevent buckling.

Another important feature of the present invention is the fact that the structural arrangement enables the use of a single, interchangeable, sensitive microswitch to obtain a large scale independent adjustment of control points. In all the prior art devices, it is necessary to use a plurality of microswitches coupled to opposite portions of the balance means for realization of the differential actuating capabilities which can be derived from an alternating fulcrum movement. Nowhere in the prior art is it realized that an alternating fulcrum move ment can be used in conjunction -with the inherent differential between distinct actuator control positions (e.g., on," off positions) of a conventional, sensitive microswitch to obtain widely and independently variable control points in terms of pressure. In other words, the almost microscopic fixed differential inherent in the microswitch is effectively made adjustable over a very large range by the mechansim of the present invention. This is accomplished by providing a single actuator, such as a push button, extending from the microswitch casing and operatively connected to the balance means at a point between the two sets of stops exclusive of the pivotal set.

The above-described combination of a single microswitch, having a single actuating button with an alternating fulcrum device, is facilitated by interposing a resilient means between the balance plate and the microswitch. The microswitch actuating button displacement will be very small when compared with the displacement of the pressure sensitive element or balance means. To facilitate the reduction of this discrepancy, the resilient means is made sufficiently weak as to absorb some of the movement of the balance means during its normal stroke. Thus, the resilient means provides an extremely simple, inexpensive lost motion connection between the balance means and the control means which is particularly suitable for use with the present type of alternating fulcrum device. Any resil- BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a view, partly in side elevation and partly in section, of a device according to one embodiment of the invention.

FIG. 2 is an exploded perspective view of most of the elements of the device of FIG. 1, certain elements being shown in section.

FIG. 3 is another exploded perspective view of the device of FIG. I including elements not shown in FIG. 2.

FIGS. 4, 5 and 6 are fragmentary sectional views of the device shown in FIG. 1, these figures illustrating various displaceable elements at different positions.

FIG. 7 is a fragmentary exploded perspective view of a modification to the embodiment of FIG. 1.

FIG. 8 is a fragmentary sectional view of a modification to the embodiment of FIG. 1.

FIG. 9 is a view partly in section and partly in side elevation of a device according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS Structural Description of Embodiment of FIGS. l6

Referring to FIGS. 1-6, in the specifically illustrated embodiment of the invention, there is shown a cylindrical housing 1 having a bottom end wall member 2 forming one wall of a sensing chamber 4. Another wall of the sensingchamber 4 is defined by a pressure sensing element herein illustrated as a diaphragm 6. The diaphragm in effect divides the housing into two chambers, namely, aforementioned lower sensing chamber 4, and upper control chamber 5. The periphery of the diaphragm is held in place, on one side, by a cylinder ring 8 secured to the housing 1 and, on the other side, by an O-ring 10 which is pressed against the diaphragm by the bottom end wall member 2. The member 2 in turn, is held in place in the housing by a snap ring 12.

While the pressure sensing means illustrated here takes the form of a diaphragm, any other suitable means such as a bellows or piston may be used.

A connection means 14, threaded to accomodate an appropriate conduit or fitting, communicates with a central passage 16 in the bottom end wall member 2. The central passage 16, in turn, communicates with the sensing chamber 4.

The upper surface of the diaphragm 6 engages a piston 18 which moves within the cylinder ring 8. Abutment prevents the piston from falling out of its cylinder and functions as a lower limit to downward movement. The piston 18 is centered in the diaphragm by an annular convolution 20 on the diaphragm formed by pressure when the device is in operation. The convolution 20 has a means diameter slightly greater than the diameter of the piston and is shaped by pressure so as to enagage the peripheral edge portions of the piston to prevent lateral movement thereof. The advantage of such a piston centering arrangement is that is affords a simple means for avoiding friction between the piston and the cylinder ring.

The housing includes an intermediate wall portion 22 which serves as an upper abutment to-secure the cylinder 8 in place within the housing 1. In the center of the intermediate wall 22, is a bore 24 passing therethrough and having a counterbore 25 at the upper surface ofthe wall 22. A pin 26 stepped in two diameters is disposed in the bore, larger diameter portion 27 being disposed within the counterbore 25. At the upper, large diameter portion 27 is a recess 28 which carries a ball 29. The ball 29 defines a pivot about which the piston is free to rotate, and this freedom of rotation facilitates formation of the convolution 20 by pressure.

Adjacent the upper surface of the intermediate wall 22 there is disposed a shim 30 of spring-like material having a symmetrical spider-like shape. The shim includes an annular outer rim 31, symmetrically arranged spokes 32 and a perforated inner hub 33. The outer rim 31 of the shim 30 is held in place against the intermediate wall portion 22 by a lower spacer member 38, but the inner hub 33 is free to move vertically along with the pin due to the resiliency of the shim material and the reduced resistance resulting from the spoked configuration. Perforated hub 33 is suitably and firmly 'attached to arecessed portion 45 of a balance plate 42, located above the shim.

The balance plate 42 has a generally disc-like configuration with a lower surface 43 and an upper surface 44. The recess 45 has a central ball receiving part with a lower concave portion 34 and anupper convex portion 35. The lower concave portion engages the ball 29 of pin 26. At points on the balance plate radially spaced from each other and near the periphery thereof are located three balls or spherical members 46, 47 and 48. Balls 46 and 47 are smaller than ball 48. Ball 46 protrudes downwardly from the balance plate, and ball 47 protrudes upwardly. Preferably, the balls are so located with respect to each other as to form the points of an equilateral triangle. The balls may be secured within holes in the balance plate by staking or, alternatively, may beformed integrally with the balance plate. The open spaces between the spokes 32 of the shim 30 are aligned with the three balls so as to permit a direct contact thereof with the intermediate wall.

Above the balance plate is a ball stop plate 50 held in place by lower spacer member 38. Also disposed above the balance plate 4.2 are a pair of coil springs 52, 53 which are connected at their lowermost ends to spring rests 54,55. The spring rests include annular shoulders 56, 57 and downwardly projecting fingers 58,59 at the lower portions thereof. These fingers 58, 59 engage complementary depressions 60,61 in the balance plate to bias the plate downwardly.

The three balls 46, 47, 48 are arranged on the balance plate so as to define a pair of axes A,B (see FIG. 2) about which the balance plate alternately pivots. Each axis is defined by two points, each point being a point of engagement of one ball with an adjacent surface. The halls are arranged so that the largest ball 48 is common to both axes, locating one of the two points defining each axis. Ball 48 and the adjacent surfaces engaged thereby are referred to as the pivotal set of stop menas.

The ball stop plate 50 includes a central opening with curved cut out portions 62,63 for} allowing the passage of the spring rests 54,55 therethrough. The section view of FIG. 1 is taken through these portions 62,63 so that the largest open area of the plate 50 is illustrated. The orientation of the balance plate 42 with respect to the ball stop plate 50 is such that the balls 46,47 and 48 are not aligned with the cut out portions 62 and 63. Thus, ball 47 will come into contact with the ball stop plate 50 upon an upward pivoting movement of the bal-. ance plate 42. The largest ball 48 is of sufficient diameter to prevent any significant vertical movement thereof between the ball stop plate 50 and the intermediate wall 22.

The upper portion of the housing includes a top closure 66 having a pair of threaded openings 68,69 therein. A pair of threaded adjustment screws 70, 71 cooperate with these openings and with the coil springs 52, 53 for adjusting the compression thereof. The adjustment screws each include a tool engaging means 72, 73 whereby each screw can be rotated to vary the vertical position thereof to adjust the associated spring. Each adjustment screw includes a recess 74, 75 at the bottom thereof, each recess receiving the uppermost portion of one of the coil springs 52, 53. Each of the two adjustment screws includes an annular rim portion 76, 77, one rim portion 77 being at the uppermost end of its respective adjustment screw 71, the other rim portion 76 being located below the uppermost portion of its adjustment screw 70. The spacing between the two adjustment screws 70, 71 is such that the rim portions of each are mutually overlapping, the rim portion 77 being above the rim portion 76. By this arrangement, it is impossible to adjust the screw 71 to a position below that of screw 70 or to adjust screw 70 to a position higher than screw 71. As the adjustment screw 70 is moved to a relatively lower position, it is clear that the compressive force on its respective coil spring 52 will be increased. Since the arrangement of the respective rims 76, 77 is such that the relative position of the adjustment screw 70 is always lower than or equal to that of adjustment screw 71. spring 52, associated with screw 70, is to be considered the high pressure spring in relation to the low pressure spring 53 associated with the adjustment screw 75.

Secured above the top closure 66 is a control means 78, preferably in the form of an electric, single pole, double throw, low differential, low force, two-position spring-return microswitch. Any suitable electrical switch or fluid controlling valve of the spring-return or toggle type could be used equally well, as long as there are provided two distinct actuation positions separated by a displacement differential, the positions corresponding to two distinct mutually cancelling control modes. By way of example only, and for the sake of convenience, these two positions and their respective control modes are referred to herein as the actuation or on position and the deactuation or off positions.

The microswitch here includes a casing 79 from which extends an actuating button 82, having one position at which the switch is actuated (i.e., the on" position) and another, different position at which the switch is deactuated (i.e., the off" position), so that an inherent displacement differential exists between the on" and off positions.

The microswitch is fastened to the housing 1 by an adjustable mount 80 which can be used to vary the vertical position of the microswitch with respect to the housing 1.

In the illustrated embodiments, an actuating post 84 between the actuating button 82 and the balance plate 42 transmits only the linear vertical displacements of the balance means to the actuating bottom. A resilient means 86 is also interposed between the actuating button and the balance plate. This resilient means will be referred to as the amplification spring." In the embodiments of FIGS. l-6, the amplification spring 86 is attached to the upper surface 44 of the balance plate 42 and is connected to the lower portion of the actuating post 84. The amplification spring 86 is made sufficiently weak so as to serve as a lost motion connecting means, reducing the amount of motion transmitted from the balance plate 42 to the actuation button 82 during the normal stroke of the balance plate and diaphragm. This reduction of transmitted balance plate motion can be said to amplify the relative inherent displacement differential of the microswitch.

In an actual working model of a device according to the present invention, the piston moves through a stroke of approximately 0.006 inches. At the same time the range of the microswitch button between on' and of points is about 0.0005 inches to 0.0015 inches. Here the amplification spring provides a simple and inexpensive means to compensate for these differences in displacement ranges.

The effective point of connection of the actuating post 84 to the balance plate is located approximately midway on a straight line between the two balls 46 and 47. Although, as illustrated, the actuating post 84 first connects with the amplification spring which, in turn, is connected with the balance plate 42, the post 84 may alternatively be directly attached to the balance plate (assuming the amplification spring has a different location). In the embodiments illustrated, the effective point of connection of the actuating post 84 with the balance means is the point at which the post 84 would engage the balance means if extended downwardly past the amplification spring. It is desirable to place the effective point of connection as close as possible to .the midpoint of the line between balls 46 and 47. This in turn, assures independence of actuating post displacements with respect to minute balance plate movements at the pivotal set of stops where both axes intersect ball 48.

The provision of, on the amplification spring 86, a portion 87 which extends away from the largest ball 48 (and thus away from the region where the two axes nearly intersect), facilitates the placement of the effective point of connection of the actuating means near the midpoint of the line between balls 46 and 47.

The possibility exists, with the use of certain types of compression springs 52,53, that they may have a tendency to buckle causing a cooking or rotation of the spring rests 54 and 55. This undesirable occurence can be eliminated by providing elongated guide members 90 and 91 surrounding and affixed to the spring rests 54,55. The guide member 900 is secured at one end to the left hand spring rest (FIGS. 1-6) and at the other end to the part of the housing shown at the right. A similar but converse arrangement exists for the guide member 91. This latter guide member is secured to the right hand spring rest 55 and the left hand portion of the housing.

When the spring rests move vertically due to balance plate displacement, the guide members rotate so that the ends nearest the spring rests move substantially vertically while the other ends remain secured in the housing. Although, strickly speaking, the movement is arcuate, this is minimized by the fact that the elongation of the guide members 90,91 is made so great as possible.

Both guide members 90, 91 and the ball stop plate 50 are secured in place between an upper spacer 92 and the aforementioned lower spacer 38. The ends of the guide members can rotate inside of elongated cavities formed by recesses 111.7 and 118 in the upper spacer and the top surface of the intermediate wall 22. Alternatively, the guides may be fastened to the stationary housing by means of suitable flexible members.

A transparent plastic cover 94 is attached to the top closure 66 to completely enclose the microswitch 78 and adjustment screws 70 and 71 to protect the same from dirt, dust or any other harmful materials in the surrounding environment.

An opening 95 through the housing 1 and upper spacer 92 together with an opening 119 in the top closure 66 serves the purpose of providing a passage for the necessary connecting cables. Opening 95 is suitably threaded for connection with a conduit.

Operation of Embodiment of FIGS. 1-6

I The operation of the device illustrated in FIGS. 13 will be described below, with reference being made to FIGS. 4, 5 and 6 showing various displaceable elements in different sequential positions.

FIG. 4 illustrates the extreme low pressure position of the diaphragm and balance plate. In this position the balls 46 and 48 are held at rest against the intermediate wall 22 by the forceof the coil springs 52, 53. Ball 47 is at an intermediate position and piston 18 rests on abutment 115. As pressure in chamber 4 increases, the diaphragm and piston will be displaced upwardly. This upward displacement will be transmitted tothe pistoz. l8 and thence to pin 26. The ball 29 transmits the motion of the pin 26 past the inner hub 33 of the flexible shim and to the concave portion 34 of the balance plate 42.'The balance plate will first begin to move against the force of the weaker of the two coil springs, namely spring 53, lifting ball 47. Meanwhile, the high pressure spring 52 will maintain the ball 46 firmly in place against the intermediate wall. The abovedescribed movement of the balance plate, therefore, is a counterclockwise pivotal movement about axis A (defined by the points of contact of balls 46 and 48 with the intermediate wall 22).

Pivotal movement of the balance plate about the axis A will continue until the upper surface of the ball 47 comes into contact with the ball stop plate 50 to retain further upward movement. At this point the balance plate is disposed in themiddle position as illustrated in FIG. 5. The balance plate will remain in this position until the pressure in the chamber 4 has increased to an amount sufficient to overcome the bias of the high pressure spring 52. At this point, the ball 46 is lifted from the intermediate, wall and moves upwardly. To permit such movement, the balance plate pivots in a clockwise direction about the axis B (defined by the points of contact of balls 47 and 48 with the ball stop plate 50). Pivotal movement of the balance plate about axis B will continue until the extreme high pressure position shown in FIG. 6 is reached.

Upon decrease in pressure, the sequence of operations is precisely the reverse of that described above. With reference to FIGS. 5 and 6 the pivotal movement about axis B from the high pressure position of FIG. 6 to the middle position of FIG. 5, as pressure decreases, is in a counterclockwise direction. After a decrease in pressure to a point at which the weaker spring 53 is able to overcome the upward force on the diaphragm, the balance plate will begin to turn from the middle position of FIG. 5 toward the low pressure position of FIG. 4, pivoting in a clockwise direction about the axis It will be understood that, at all times when the balance plate pivots about the axis A, the line of force of the high pressure spring 52 will be acting directly through that axis, so that the high pressure spring is rendered ineffective, exerting no influence on the pivotal movement of the balance plate. Likewise, during movement of the balance plate about the axis B, the low pressure spring 53 acts directly through that axis and is rendered ineffective, exerting no influence on the pivotal movement.

The above described alternate pivotal movements of the balance plate effect only a linear displacement of the actuating post 84. The motion is transmitted from the balance plate to the actuating post 84 via the amplification spring 86 which serves as a lost motion connection. The linear movement of the actuating post is transmitted to the actuating button 82 of the microswitch 78 for actuation and deactuation thereof.

As discussed above, there is an inherent displacement differential between the position of the actuating button at which actuation of the micro-switch is effectuated and the position at which deactuation is effectuated. This inherent differential between on and off points is common in known microswitches and other similar control means.

In the device of the present invention, the vertical position of the microswitch 78 with respect to the housing 1 is adjusted so that the middle position of the balance means, as illustrated in FIG. 5, corresponds to the middle position in the inherent displacement differential of the microswitch. In other words, with the balance plate in its middle position, the microswitch actuating button is midway between the actuation and deactuation points.

By way of example only, it will be assumed that the deactuation or of point of the microswitch corresponds to the vertically lower actuation button position in relation to the on" point. As described above, assuming the balance plate to be in the low pressure position and the microswitch in the off" position, as pres sure increases in the chamber 4, the balance plate 42 pivots about the axis A until reaching the middle position. With sufficient additional increase in pressure, the balance plate then begins to pivot about axis B. During this latter pivotal movement, the post 84 will cause the button 82 to pass through the actuating position moving the switch to the on" position.

As also described above, a pressure decrease causes the balance plate to move back to the middle position by pivoting about axis B. Then, after sufficient decrease in pressure, the balance plate begins to pivot about axis A toward the lower pressure position. During this latter pivotal movement about axis A, post 84 causes the button 82 to pass through the deactuation point moveing the switch to the of position.

It will be understood that the values of pressure at which the micro-switch is moved into the on and of positions are determined by the adjustments to the biasing forces of the springs 52,53. To obtain a very wide pressure differential between onand off points, the high pressure spring 52 is adjusted to exert a very high biasing force. This is accomplished by moving the adjusting screw 70 to a relatively low position. At the same time, the low pressure spring 53 is adjusted to exert a relatively weak biasing force by moving the adjusting screw 71 to a relatively high position. With such an adjustment, assuming all the elements to be in their extreme low pressure positions, a very small increase in pressure causes the balance plate and microswitch button to move into their middle positions at a very low pressure. The balance plate and switch button remain in this middle position over a large range of pressure increase until the pressure reaches a value near the maximum. At this high pressure, the force of the high pressure spring will finally be overcome to actuate the microswitch.

With only a small pressure drop, the balance plate and switch button again return to their middle positions but the microswitch remains in the oncondition. After a large pressure drop to a point near the minimum pressure, the balance plate begins to pivot from its intermediate position toward its low pressure position for deactuating the microswitch to the of condition.

it will be clear that a setting of the adjustment screws, whereby little difference exists between the bias on the low pressure and high pressure springs, creates a condition wherein the balance plate remains in the intermediate position only during a very small pressure change. With this condition, therefore, the pressure differential between on and off positions of the microswitch is likewise very small. Also, it will be clear that, by adjustment of. the biasing force on the springs, the higl. pressure on point and low pressure off" point can be adjusted to practically any point within the overall range of operation of the device.

Modification According to FIG. 7

FIG. 7 shows an alternative embodiment wherein the ball stops, rather than being secured to the balance plate, are located separately therefrom. Whereas, in the previously discussed embodiment, the complete stop means included the combination of the three balls on the balance plate, plus the lower, intermediate wall 22, plus the upper, ball stop plate 50; the complete stop means in the present embodiment includes the balance plate itself plus a set of balls adjacent both the upper and lower faces of the balance plate. Whereas in the previously described embodiment, movement of the balance means caused the balls thereon to alternately come into contact with the intermediate wall and ball stop plate, in the arrangement of FIG. 7, the balance plate itself comes into contact with stationary balls disposed on either side thereof. In the embodiment according to FIG. 7, elements which are substantially identical with the corresponding elements in FIGS. 1-6, are indicated by the same reference numerals.

In FIG. 7, a set of three balls or spherical members 101, 102 and 103 are located in corresponding holes of a ball guide 108. The halls are held in place both by the ball guide 108 and the intermediate wall 22 located therebelow.

Balls 101, 102 and 103 together with guide 108 are disposed below the shim 30 and balance plate 42. When the balance plate is in its extreme low pressure position, it will rest against all three balls 101, 102 and 103.

Disposed above the balance plate are two additional balls or spherical members 110 and 111 located in holes in an upper ball guide 114. Directly above the guide 114 is the ball stop plate 50. Both the upper ball guide 114 and ball stop plate are effective to hold balls 110 and 111 in their proper positions. The upper ball guide 114 includes cut out portions 115 and 116 substantially identical to, and aligned with, the corresponding cut out portions 62, 63 of the ball stop plate 50. These cut out portions permit passage of the spring rests 54, therethrough so that the fingers 58, 59 thereof may engage depressions 60, 61 of the balance plate 42. The balls 111 and 102 are aligned vertically with each other and are so spaced from each other as to preclude any substantial vertical movement of the balance plate 42 therebetween. The function of the balls 111 and 102, together, is analogous to that of ball 48 in the previously described embodiment. Each of the alternating axes, shown as A and B in FIG. 7, pass through the vertical line between balls 102 and 111.

Ball 101 serves merely as a stop or rest for the balance plate 42 when it is in its lower pressure position. Ball 103 also serves this purpose, but, in addition, also serves to partially define the axis A about which the balance plate pivots during the initial stroke of the diaphragm. The axis A is fully defined by the points of engagement of the balls 102 and 103 with the balance plate. The fact that the shim 30 has spokes 32 between the outer rim 31 and hub 33 permits the balls 101, 102 and 103 to protrude through the open spaces between the spokes and engage the balance plate.

The pivotal axis B is defined by the points of contact of balls and 111 with the upper surface 44 of the balance plate 42. Ball 111 is larger in diameter than ball 110 and it may continuously engage the balance plate at all times (but it is also possible that a very small clearance may, at times, exist).

Operation of Modification According to FIG. 7.

In operation, assuming that the balance plate is at its extreme lower pressure position and is held against balls 101, 102 and 103 by the force of springs 52,53, an increase in pressure will cause the balance plate 42 to be lifted against the bias of the low pressure spring 53. The balance plate 42 will move vertically upwardly away from ball 101 while pivoting about the axis A. This movement continues until the upper surface of the balance plate comes into contact with ball 110, which is vertically aligned with ball 101. At this point further pivotal movement about the axis A is prevented. With a sufficient additional increase in pressure to overcome the force of high pressure spring 52, pivotal movement about the axis B will commence. This movement will continue until the extreme high pressure position is reached. Movement from the high pressure position to the low pressure position upon decrease of pressure is precisely the reverse of that described above.

In the embodiment of FIG. 7, the operation of remaining elements is the same as that of the corresponding elements of the embodiment of FIGS. l-6. Modification According to FIG. 8

FIG. 8 shows a modification to the balance plate and ball arrangement of FIGS. l-6. Rather than providing a single ball 48 stacked into the balance plate so as to extend from both the top and bottom surfaces thereof, balls 120 and 121 are provided on either side of a simple chambered hole 124.

The use of balls, as elements of the complete stop means in all of the above-described embodiments, is highly advantageous, since balls can be easily manufactured to very close tolerances. This is important here, where the displacements involved are very small. Also, the fact that metal balls can easily be hardened is important where, as here they will be subjected to considerable wear.

Embodiment According to FIG. 9

FIG. 9 illustrates an additional embodiment of the present invention utilizing a beam 150 in place of the balance means 42 of the previously described embodiments. Here, tension springs 152, 153 are used in place of the compression springs 52, 53 of the other embodiments. The same type of microswitch 78 and actuating bottom 82 therefor are used with this embodiment. As in the embodiments of FIGS. l-8, a pressure connection 14 communicates with a chamber 4 defined by a bottom end wall 2 and a diaphragm 6. The diaphragm is attached to a piston 18 which in turn is connected to an elongated vertical rod 155 engaging the central portion of the balance beam 150. Each end of the balance beam includes recessed portions 158 and 159, each recessed portion being effective to provide a pair of downwardly facing surfaces 160 and 162, 163 and 165 at its respective end. Tension coil springs 152 and 153 are connected near the ends of the balance beam adjacent the lowermost of the downwardly facing surfaces 162, 165 at each end. The uppermost of the downwardly facing surfaces 160, 163 are adapted to engage with stop means 168, 169 secured to the housing.

Tension spring 153 is adjusted to be the lowpressure spring and tension spring 152 is adjusted to be the high pressure spring. The arrangement is analogous to that of compression springs 52 and 53 of the embodiments previously described. An additional stop 171 is located on the side of the balance beam to which low pressure spring 153 is attached and is positioned to engage an upwardly facing top surface 173 on the balance beam. The arrangement of the springs and stops is such that, on each end of the balance beam, the line of force of the respective tension spring coincides with the point or points of contact of the respective stop or stops with the corresponding surface or surfaces of engagement on the balance beam.

In the same manner as the balls and their respective surfaces of contact formed points defining the alternating axes of the embodiments of FIGS. l-8, the points of contact of the stops 168 and 171 with the surfaces 160 and 173 define the fulcrum points about which the balance beam 150 alternately pivots.

Operation of Embodiment of FIG. 9

The operation of the device of FIG. 9 is as follows:

Assuming the diaphragm 6 is in its extreme low pressure position, the downwardly facing surfaces 160 and 163 will rest against stops 168 and 169. As pressure increases and the diaphragm moves upwardly, surface 163 of the balance beam will be lifted off stop 16 against the resistance of the low pressure spring 153. At the same time the surface 160 will be held against stop 168 by the bias of high pressure spring 152 so that the balance beam pivots about the fulcrum defined by the point of contact of surface 160 and stop 168. This pivotal movement continues until the surface 173 engages the stop 171, at which point the balance beam is in its middle position. When the pressure increases sufficiently to overcome the tension of high pressure spring 152, the balance beam will begin to pivot about the fulcrum defined by the point of contact of stop 171 and surface 173. This pivoting movement continues until the high pressure position is reached. From this position the reverse alternating fulcrum movement takes place as the pressure decreases and the balance beam returns toward the lower pressure position illustrated in FIG. 9.

It will be appreciated that the stops 168 and 171 define the fulcrum points for the alternating pivotal movement of the balance beam. It will be further appreciated that these fulcrum points are aligined with the line of force of the adjacent tension spring. In this way, the spring adjacent a given fulcrum is rendered completely ineffective during rotation of the balance beam about that fulcrum. Therefore, similarly to the situation in the other embodiments, the individual springs 152 and 153 operate completely independently of each other.

It will be understood that in the embodiment of FIG. 9, the operation of the microswitch with respect to the movement of the balance beam is identical to the operation thereof with respect to the movement of the balance plate 42 in the other embodiments. Thus, the device illustrated in FIG. 9 possesses the same capabilities of full-scale independent pressure differential and pressure range adjustment.

Overpressure Protection In none of the embodiments of the present invention, has there been illustrated or described a stop or abutment to restrain the pivotal movement of the balance means asit approaches its extreme high pressure position. It is intended that the position at which piston 13 contacts the intermediate wall 22 is to be considered the extreme high pressure position. Thus, in the event that the device is subjected to overpressures, the piston 18 and wall 22 will be able to withstand the forces thereof. If, on the other hand, a stop means associated with the balance means were to define the high pressure position, a significant overpressure in the chamber 4 could result in serious damage to the balance means.

In the embodiment of FIG. 2 this possibility of damage is prevented by having ball 46 protrude downwardly, leaving sufficient space between the balance plate and stop plate 50. In the embodiment of FIG. 7, the same result is obtained by the absence of a ball above the balance plate at the left hand, high pressure side. In FIG. 9, the override protection is obtained by the absence of a stop above the balance beam near the upper high pressure side.

Fixed Differential It is possible to convert the pressure switch of the present invention to operate as a fixed differential device. In such a device the displacement difference between the on" and of points is relatively constant but the overall pressure range may be adjustable.

In the embodiments of FIGS. l-8 this is accomplished by elimination of the low pressure spring 53, its associated adjustment screw, spring rest and guide. With such an arrangement, a negligible pressure will cause the balance plate to move into the middle position of FIG. 5. This constitutes the low pressure position, and any substantial variations in pressure will cause the balance plate to pivot about the axis B. The position of the microswitch is adjusted so that both the actuation and deactuation to and from the on and of points takes place entirely during the pivotal movement of the balance plate about axis B.

The same result is obtained in the device of FIG. 9 by eliminating the low pressure spring 153 and its associated adjusting screw. Here actuation and deactuation takes place during the pivotal movement about stop 171.

While throughout the above description words such as vertical, upper, lower, upwardly, downwardly, right and left have been used, it will be understood that these terms are used only to describe relative relationships and are not intended to be limiting. it will also be understood that those skilled in the art may make many changes and modifications to the above-described embodiments of the present invention without departing from the spirit and scope thereof.

What is claimed is:

1. A control device comprising:

a. a housing;

'b. a chamber in said housing;

c. a displaceable sensing means defining a wall of said chamber;

d. first and second compressible coil springs disposed in said housing and operatively connected to said sensing means, whereby displacement of said sensing means flexes said springs;

e. a first guide means one end of which is connected with said first spring, the other end of said first guide means being connected to said housing at a first connection point;

f. a second guide means, one end of which is connected with said second spring, the other end of said second guide means being connectedto said housing at a second connection point;

g. said first connection point being located in said housing remotely from said first spring and adjacent to said second spring, said second connection point being located in said housing remotely from said second spring and adjacent to said first spring, whereby arcuate movement of said guide means during flexing of said springs is minimized.

2. A control device as defined in claim I wherein said first connection point is disposed substantially'diametrically opposite to said second connection point. 

1. A control device comprising: a. a housing; b. a chamber in said housing; c. a displaceable sensing means defining a wall of said chamber; d. first and second compressible coil springs disposed in said housing and operatively connected to said sensing means, whereby displacement of said sensing means flexes said springs; e. a first guide means one end of which is connected with said first spring, the other end of said first guide means being connected to said housing at a first connection point; f. a second guide means, one end of which is connected with said second spring, the other end of said second guide means being connected to said housing at a second connection point; g. said first connection point being located in said housing remotely from said first spring and adjacent to said second spring, said second connection point being located in said housing remotely from said second spring and adjacent to said first spring, whereby arcuate movement of said guide Means during flexing of said springs is minimized.
 2. A control device as defined in claim 1 wherein said first connection point is disposed substantially diametrically opposite to said second connection point. 